cannot see the geometry of the imported stl file
The STL will import in the position of the 3D cursor using the origin point of the STL object - the little orange dot. In theory that is the absolute centre 0/0/0 in the X/Y/Z. Some models are created far from their origin and while they might appear not to be there, they might actually be off screen.

Make sure the object is select the object in the Outliner...



Before trying scaling - set the origin to the geometry...



With the object still selected press ALTG which will move the object back to 0/0/0.

Another possibility: Blender STL [both import &amp; export] have a scaling approach which makes [most] STL files prepared in other applications one thousand times larger - here too, they could have imported, but are not visible...yet.

In either case pressing the Home button on the keyboard, will show everything in the scene - if it jumps back and turns grey it just means it has exceeded the visible parameters, and as suggested, you will need to expand the View clip values.